Physical Model Test On Working Mechanisms Of An Anchor Group System With Wood Bolts In Rammed Earthen Sites

As one of the most important architectural types of human civilization,rammed earthen sites in the northwest China are the carrier of important information such as history,culture and science.With the change and progress of the times,rammed earthen sites are suffering from human activities and the destruction of natural environment and other factors.As an important reinforcement measure of the earthen sites,anchorage technology has been gradually applied to the protection projects of earthen sites.Based on the principle of "No changing the original state" and "Using local materials",wood bolt has been widely used in earthen sites anchorage technology because of its good compatibility.At present,the research on anchoring mechanism of rammed earthen sites mainly focuses on single anchor,while the research on anchoring mechanism of group anchor is just beginning,which severely limits the development of anchoring technology of earthen sites.In this paper,the most basic two-anchor system in the group anchor system of rammed earthen sites is selected as the research object,and the anchorage mechanism of two-anchor system of earthen sites is studied from multiple perspectives by using different models and ways.The anchorage mechanism of the two-anchor anchorage system of wood anchor was studied by reducing scale test and indoor model full scale test,and by using drawing test system and displacement monitoring system.The anchorage mechanism is further discussed by numerical simulation software and digital image technology.In order to have a deep understanding of the anchorage performance and interfacial mechanical characteristics of the two-anchor anchorage system in rammed earthen sites.Through the above studies,the main conclusions of this paper are as follows:(1)The results of digital image test show that the transverse and longitudinal displacements of the horizontal and vertical measurement lines are continuously changing under different loads,and the longitudinal displacements of the observation points on the horizontal measurement lines are parabolic,while the lateraldisplacements of the observation points on the vertical measurement lines are conical.(2)According to the test,the failure mode of the anchorage system is the upper cone failure,while the lower part is only the compound failure of the bolt pulling out.It is of referential significance to how to improve the anchorage strength in construction.(3)The load displacement curves obtained in the model test and numerical simulation are both in the elastic stage at the early stage of loading and in the plastic stage at the late stage of loading.(4)When the bolt spacing is less than 0.458 m,the spacing effect begins,while when the bolt margin is less than 0.228 m,the spacing effect begins.The two parameters of margin and spacing have a significant influence on the pull displacement of wood bolt.Under the same load,the smaller the margin and spacing,the greater the pull displacement of the wood anchor,and the more obvious the margin effect and spacing effect.(5)Parameter analysis shows that in the pulling test of soil sites,when the bolt spacing is less than 0.458 m,not only the spacing effect but also the effect of reinforcement.The reinforcement effect should be considered,which can reduce the displacement of the bolt.The point where the spacing effect and the edge effect occur in actual engineering is the most suitable construction position of the anchor.